DE1615448B1 - Device for processing materials by means of an electron beam - Google Patents

Description

1 2

The invention relates to a yawing or parallel electron beam device

for the processing of materiahen by means of an elec- to generate; the space charge constant results

tron jet, with an airtight container, which is made up of the ratio of jet direct current to jet

through at least one opening for passage DC voltage high 3/2.

of the electron beam having partition in 5 The object of the invention is therefore to provide a device

to specify an electron delivery source receiving device of the type mentioned, which it

a first evacuation pump to be connected allows an electron beam with relatively

mer and a large cross-section of a second evacuation pump and therefore relatively large

to be connected processing chamber is divided, ßer performance on a material to be processed

and direct with a device generating a magnetic field without the pumping power of the vacuum

device for the direction of the electron beam on the pumps must be kept uneconomically large.

Opening. To solve this problem, the device

Devices of this type are characterized in that a homogeneous nen material processing methods applied, such as and parallel magnetic field generating device in the case of melting, annealing, cleaning, vapor deposition, 15 it is provided that the electron-donating source Plating, etc. Usually contains one and the opening or openings therein Device focusing devices, with the help of a magnetic field, are located that the cross-section of the Elekderer the electron release surface of the electron release source in Benen electrons are bundled on the respective shape and size of the cross-section of the opening material to be processed. This measure - or the openings - is the same and that the strength material is together with the electron of the magnetic field, the speed of the electrical output source in a closed, evacuated and the distance between the electron container. To focus the electrons on a delivery surface of the electron delivery source and the Electron beams can be electrostatic or opening - or between the openings - so magnetic Apply fields. The electrons of the 25 gauge are that the electrons are on their helical electron beam meet the shaped path to be machined between the electron delivery source Material and heat it. From the heated and the opening - or between the openings - In the process, gases and vapors enter the material and make various complete circuits.

of the greatest kind. These gases can be in the area due to the homogeneous and parallel magnetic field

the focussing fields to arc discharges 30, the electrons are released from the elec-

lead if they are not directly from the vacuum electron delivery surface of the electron delivery source

can be withdrawn. moves in a helical path and generates in

It is known that the developing gases with the opening or in the openings virtual exhaust

With the help of vacuum pumps, which take a picture of the electron-donating surface. The opening or

Have sufficient capacity to make the most of 35 the openings are used optimally, so

to divert gas escaping from the heated material. that the vacuum pump output is optimally low

Such pumps are expensive and unwieldy. can be held.

As an electron delivery source it is in cases, in comparison with the known devices with large

for whom a high performance is required, it is known that the electron-donating surface has the advantage,

So-called "Pierce" electron slingshots between the electron-donating surface and the

turn around. A Pierce electron gun contains at least one screen to be processed

usually an electron donating surface to be arranged or a ridge with an opening.

through an indirectly or directly heated cathode Compared to known devices with magnetic

can be formed. The shear focus emitted by the cathode results in the advantage of the large

Electron beam is generated with a focussing surface and thus the large elec-

Electrode and an anode influenced in such a way that it electron beam power.

receives the desired shape, z. B. a round, The invention is hereinafter with reference to

rectangular or some other shape. The form drawings explained in more detail.

of the electron beam is through openings in FIG. 1 shows schematically in a cross-sectional

Focusing electrode and determined in the anode. 50 views an embodiment of the invention

The focusing electrode, which is on the same electron beam device, on hand

Potential lies like the cathode, from which the various features of the invention run

Cathode can be explained from under an opening angle of about;

67Va ⁰ , based on the axis of the desired F i g. 2 shows schematically an enlarged transverse

Electron beam, outwards. The anode of the elec- 55 Sectional view of an electron centrifuge, which in the

The electron gun is offset from the cathode - the electron beam device shown in FIG. 1

arranges; it runs from the edges of the desired can be applied;

Electron beam under a predetermined win- Fig. 3 shows schematically in a cross-sectional

kel to the outside. The arrangement of focusing looks at a further embodiment of a different

electrode and anode is usually critical. 60 unite the features of the invention

If the anode is too close to the cathode, the electron beam device is removed.

stands a diverging electron beam, the nor- The electron beam shown in Fig. 1

is sometimes unusable. For a higher direction an airtight sealed cover contains

Electron beam current, however, it is necessary, the container 10, which is separated by two separators 18 and 20 in

Arrange anode close to the cathode. Thereby 65 has three chambers 12,14,16 is divided. In one

it turned out to be difficult to load an outer electron chamber (electron centrifugal chamber 12)

slingshot with a higher space charge constant there is an electron release source or elec-

to create a 0.5-ΙΟ " ⁶ with a converter spinner22; in the other outer chamber

3 4

(Processing chamber 16) there is a target shape, cylinder shape, etc. The container 10 is made of material 24, which represents the material to be processed - two separating webs 18 running parallel to one another. In each of the separating webs 18 and 20, one and 20 are divided into three chambers 12, 14, 16. The opening 26 and 28 respectively included. These openings are partitions and can be any suitable mazur axis of the ab- 5 material from the electron gun 22 which directs the given electron beam prevailing in the container. With the aid of temperatures and the prevailing environment the device 30 is able to withstand a homogeneous magnetic field.
generated parallel to the axis of the electron beam according to FIG. 1 is in the middle part of each one. The electrons emitted by the electronic separating web 18 and 20 move a circular plate 38 electron thrower 22 on io or 40 made of ferromagnetic material, such as steel, helical paths to the openings 26 and. The distance between the separators 18 and other material, such as copper. In the middle of FIG. 20 and between the separating web 18 and the electrical plates 38 and 40, there are ejected centrifuges 22, which are largely identical to aligned openings 26 and 28, and the number of revolutions of the helical path 15 will be discussed in greater detail below will. The respective parts on which the electrons move are selected as plates 38 and 40, which form separating webs, are used. Pumps are connected to the chambers 12, 14 and 16 as pole pieces when generating a homo device 32, 34, 36, which are used to generate the magnetic field in the intermediate or through evacuation of the respective chambers. passage chamber 14. This homogeneous magnetic field

If an electron moves parallel to a homo- 20 runs parallel to that between the openings 26 and its own magnetic field, it is not deflected; there 28 extending axis. To generate the subject therefore moves along a straight line. When there is a magnetic field, the relevant electron is provided in a right-hand coils 42, which are arranged between the outer sides at an angle to the relevant homogeneous magnetic field of the plates 38 and 40,
moving direction, it is on a 25 As F i g. 1 reveals that the Elek orbit is deflected. If an electron moves into an electron release source or electron ejector 22 in between the two directions just considered of the one end chamber, which is also referred to as the horizontal direction below, its loading corresponds to electron ejection chamber 12, which is designated. In the trajectory of a helical line, the axis of which is parallel to this chamber, the electron lock in question runs parallel to the magnetic field in question. Electrons arranged in such a way that an electron field line can be emitted at the same angle but radiated along the axis connecting the opening trons, the axis connecting a point on a magnetic gene 26 and 28. Leaving the electron in different directions, any straight electron field line can occur simultaneously on the sling 22 at a point that is only sling, but preferably one that is suitable for the delivery of high output currents by the distance of one revolution of the helical line 35, ( Slope) is offset. The slope of the subject like a Pierce electron gun. The electron spiral line depends on the cosine of the angle of the slingshot 22 is at a suitable distance from the separation deviation of the electrons from the field lines. web 18 is arranged and is located in the At small angles, the slope only changes the central opening of a pole piece 44, which is similar to hardly any change in the angle. Is a 40 the plates 38 and 40 can be formed by a plate of ferro-magnetic field parallel to an electron beam of magnetic material,
directed, all electrons move between the electron gun 22 and the same direction; the electron opening 26 in question is generated with the help of an iron coil 46, which emerges from the starting point in a corresponding arrangement 45 between the outer sides of the plates 38 and 44 on the slope of the helical line, a homogeneous magnetic field, was offset on the electron beam axis on. Due to this homogeneous field, the surface generated by the electron discharge emission surface of the electron thrower 22 after one or more revolutions or given electrons are directly influenced, and the inclines of the helical line along the line are such that they exit the emission -Field lines moved electrons an image. The surface is located on a helical path for the length of one revolution or slope of the helical path and for every whole number of revolutions lines is the same or gradients of the helical path

/ 77 of the emission area.

21.2-10 "] / Kcosfc> _{The distance} between pole pieces 38 and 40

B 55 and the distance between the emission surface

the electron spinner 22 and the pole piece 38

Here, V means the electron speed are chosen so that an image of the emission levels in volts, B the magnetic flux density in Wb / m ² area just in each of the openings 26 and 28 is generated and Θ the deflection angle, based on the field. Here is the distance between the opening lines. 60 editions 26 and 28 and between the emissions cap

In the case of the execution area shown in the drawing and the opening 26 selected so that in

For example, the production of images will be the same number of revolutions in both cases

of the emitting surface used for this purpose, which gives rise to or slopes of the helical path.

Amount of reaching the electron ejector As mentioned earlier, is called an electron ejector

To reduce gases or vapors. The in F i g. 1 65 22 preferably a Pierce electron gun

includes the electron beam device illustrated as used. Such an electron centrifuge

mentioned, the airtight container 10 manufactures a high jet flow, whereby the on the

which has a suitable shape, like a rectangular material to be machined 24 heating power

5 6

is correspondingly high. As shown in Fig. 2, the amount of penetration of gases and vapors through contains the Pierce electron gun in the dar- the opening 26 is particularly small, since with normal Embodiment provided an emission surface operating pressure in the chambers 12 and 14 through the or cathode 48 in the form of an elongated cylinder opening 26 instead of a normal viscous stream or filament made of a suitable material, such as 5 mes a so-called molecular current passes through. Tungsten. This filament creates a corresponding flow rate of gases and correspondingly high current passed through. Considerable in certain fumes through the outlet openings Turn cases can also erne indirectly heated from as soon as a pressure is reached at which a mol-cathode be used. Two plates 50 and 52, a circular flow occurs instead of a viscous flow, which together serve as a focusing electrode, io This pressure is so great that the middle free run from the cathode 58 under an OfE path length of the vapor or gas molecules the same or angle of each 67V2 °, based on which is less than the distance between the sides of the Electron beam center line; the two plates outlet openings. The molecular flow of the gases 50 and 52 consist of a temperature-resistant one due to an outlet opening is about 43% lower gen material. A suitable material for this is 15 as the tungsten through the same outlet opening or tantalum. The focusing electrodes are discharged from viscous electricity. Using a can occur as a plate with an opening 26 therein in the form of a narrow rectangle Be formed slot for receiving the cathode. the molecular current at higher pressure than at The cathode 48 and the two focus plates use a circular opening similar to one another 50 and 52 are at a high negative potential, the area size 20. This leads to a considerable is supplied by a voltage source 54. Reduction of a certain pressure

In the embodiment shown, the difference is upright on both sides of the opening.

Anode of the electron centrifuge from two metal-retaining vacuum pumps; Expressed differently

rods 56 and 58, which run parallel to the cathode, this means that it is hereby possible to open

and on both sides of the electron beam with a larger cross-sectional area for a given

are arranged. The rods that are slidably arranged to use pump size.

The target material to be machined, which can be a metal material such as tungsten space, tantalum, etc. The rods or a non-metal is suitably 56 and 58 and likewise the pole pieces 44, 38, 40 and in the processing chamber 16 arranged, the target material 24 are grounded. As mentioned above, the electron emerging from the last opening 28 is forced to guide the electron beam is no longer troned by the magnetic field as soon as it is influenced by the magnetic field, whereby it emerges as a result of the charge cathode; thus there is a divergence that divides the repulsion. The position of the target material, which prevents electrons. This permits the use of the last opening 28, depends on the work processes to be carried out on the target material by means of adjustable rods as anodes and the use of a relatively small amount and on the level of power expended. Distance between the anode and the cathode The closer the target material to the imaging point and thus the higher the beam current. Without the electron beam being shifted, the stronger the magnetic field would be. In order to melt the target material 2 .. B., lead a beam that would normally be unusable. The electron beam is normally distributed over its The magnetic direction also spreads the amount over the entire surface in order to avoid hot spots of the electrons hitting the anode.

whereby, even with high currents, a different order of the in the intermediate chamber and in the elec-

Anode cooling as the amount of penetration caused by radiation

Cooling is not required. Reducing ions and metal vapor can do that

As an image of the emission surface in the target material can be arranged in such a way that it does not have to Openings 26 and 28 are created, the openings have the openings 26 and 28 aligned. The out openings 26 and 28 have the same shape as the electron beam exiting the opening 28 trönenäbgabeöbex area. In addition, these openings are then to be worked on by a transverse magnetic field 26 and 28 are rectangular, as tend target material is deflected out; this transverse magnet too the cathode is rectangular in shape. The field is controlled by a suitable device (not Edges of openings 26 and 28 are beveled (shown) created behind the last opening 28 to prevent the electrons from being placed on the pole. By electron bombardment of the target 38 and 40 hit. The bevels 55 materials generated vapors and ions therefore collide however, they are not critical. rather on the separator 40 than that they through

As a result of the electron beam impinging on the opening 28, pass therethrough.

the target material 24 is heated to this; This ent- The chambers 12, 14 and 16 are marked with "Help gases and vapors wrap around. The separating webs 40 of suitable pumps 32, 34, 36 are evacuated. For educational and 38 reduce this to a considerable extent Amount of chamber 12 most strongly evacuated into the electron ejection chamber 12, d. H. to a entering gases and vapors. The gases and vacuum of more than 0.1 microns of mercury Vapors can only be brought in through openings 26 and 28. Due to the shown Vorin enter the electron spinning chamber 12. Since the direction of the existing pressure separation system occurs the openings 26 and 28 in the shape and size of the 65 only a very small amount of steam or gas The shape and size of the electron delivery surface from the processing chamber 16 into the electron speech, occurs only a relatively small "loss of centrifugal chamber 12. In this way, with of gases and vapors between the chambers. With the help of a high-speed diffusion pump of the

in small quantities occurring vapor flow from the Electron centrifugal chamber 12, in which a high vacuum prevails, to be eliminated.

The level of pressure prevailing in the processing chamber 16 depends on that on the target material 24 executing machining process. When performing normal machining operations the processing chamber is preferably evacuated so quickly that a sufficiently rapid discharge of vapors occurring during the execution of the relevant machining process and gases. This results in a relatively low vacuum in the processing chamber 16 because the electrostatic high-voltage fields are not present here. Therefore, a High pressure pump, like a mechanical vacuum pump, for evacuating the processing chamber 16 can be used.

In the passage chamber 14 there is a vacuum that is between that in the processing chamber 16 and the vacuum prevailing in the electron centrifugal chamber 12. The allowable pressure difference between the chambers depends on the amount of gases evolving. For low For quantities of gases, a pressure difference of up to about 100: 1 is permissible. In certain applications, the passage chamber can be omitted will. With large amounts of gases evolving, the pressure difference is preferably not greater than 10: 1 selected. In order to achieve a lower pressure difference across the dividers, additional passage chambers can be provided.

In an illustrated embodiment of the electron beam device, the emission surface has a width of about 3.2 mm and a length of about 22.2 mm. The openings in the Separators are approximately 3.2 mm wide and 25.4 mm long. The pole pieces are made of steel and are spaced about 203 mm apart. The magnetic field density is 108 Gauss at 10 kV electrons and 130 Gauss at 15 kV electrons. The electron spin chamber is set to 0.6 microns Mercury evacuated, the intermediate chamber to 17 microns of mercury and the processing chamber on 100 microns of mercury.

In the case of the in FIG. 3 embodiment shown, in which with in F i g. 1 matching elements Elements are identified by corresponding reference symbols with a subsequent index »α« net, the magnetic field is generated by "Helmholtz" coils 60, 62, 64. Helmholtz coils are coaxial air-core coils, which are arranged offset in such a way that the distance between the coil centers equal to the mean diameter of the coils. The separators 18 a and 20 a between the Chambers 12 a, 14 a and 16 a are also made of a non-magnetic material, such as from water-cooled copper.

The Helmholtz coil system according to FIG. 3 has, compared to the one shown in FIG. 1, ferromagnetic System two main advantages. The first major advantage is that the magnetic lines in the openings are not curved, but are straight and parallel, and unaffected by the Presence of an outlet opening or its thickness. In the embodiment shown in FIG The electrons therefore do not run into an area in which the magnetic Field lines do not run parallel, but diverge on one side of the opening and on the other Side converge. The non-parallel field lines can be the electrons in the electron beam influence unequally; this depends on the position of the electrons in the opening. The second The main advantage is that the inductive resistance of the air core coil is much lower than that the iron core coils. As a result, the magnetic field density can be chosen to be significantly higher than through an adjustment system. In this way, any changes in the amount of the Electron centrifugal cathode prevailing potential be balanced. Thus, the electron beam always be kept directed towards the opening.

The invention thus provides an electron beam device that is effective Use of powerful space charge electron slingers is permitted, which is normally the case generate unusable, diverging electron beams. Furthermore, in the invention Apparatus relatively cheap pumps are used to get what is required in the system Maintain vacuum.

It should be noted that, in deviation from the embodiment shown in the drawing, in which only one electron gun is used is also more than one electron gun with associated openings in the separators can be provided. Furthermore, as mentioned above, it can be used in certain applications it may be desirable to use only one divider, i. H. a divider that holds the vacuum container divided into two chambers, namely an electron centrifugal chamber and a processing chamber. Furthermore, in some cases it may be desirable to have more than three chambers. Various other changes and modifications can be made in the above Electron beam apparatus can still be made without departing from the general teachings of the invention is deviated.

Claims (8)

Patent claims: 1. Device for processing materials by means of an electron beam, with an airtight Container through at least one opening for the electron beam to pass through having a partition into an electron discharge source receiving, to a first evacuation pump Chamber to be connected and one to be connected to a second evacuation pump Processing chamber is divided, and with a magnetic field generating device for directing the electron beam onto the opening, characterized in that, that a homogeneous and parallel magnetic field generating device is provided that the electron delivery source (22; 22 a) and and the opening or openings (26, 28; 26 a, 28 a) in this magnetic field are that the cross section of the electron-donating surface of the electron-donating source (22; 22 a) in shape and size to the cross section of the opening - or the openings (26, 28, 26 a, 28 a) - and that 009 550/201 the strength of the magnetic field, the speed of the electrons and the distance between the electron delivery surface of the electron delivery source (22; 22 a) and the opening - or between the openings (26, 28; 26 α, 28 α) - are dimensioned so that the electrons on their helical path between the electron delivery source (22; 22 a) and the opening - or between the openings (26, 28, 26 a, 28 a) - make whole rounds. . 2. Device according to claim 1, characterized in that the linear cross-sectional dimensions of the opening or the openings (26, 28; 26 a, 28 a) are dimensioned such that they are small compared to under normal operating conditions the free path of the gases contained in the chambers (12, 14, 16; 12 a, 14 a, 16 a) are. 3. Apparatus according to claim 1 or 2, characterized in that the electron donation surface the electron delivery source (22; 22 a) and the cross-sectional area of the opening or openings (26, 28; 26 a, 28 a) are rectangular. 4. Device according to one of the preceding claims, characterized in that the ratios the pressures of adjacent chambers (12, 14, 16; 12 a, 14 a, 16 a) between 10: 1 and 100: 1. 5. Device according to one of the preceding claims, characterized in that the Partition wall (18, 20) made of ferromagnetic material and the pole piece of an electromagnet (42, 46) forms. 6. Apparatus according to claim 5, characterized in that that the "electron delivery source (22) in an opening of a pole piece of a Electromagnet (46) forming plate (44) is arranged from ferromagnetic material. 7. Device according to one of the preceding Claims, characterized in that the electron delivery source (22; 22 a) as a Pierce source is trained. '- 8. Device according to one of the preceding claims, characterized in that the Magnetic field generating 'device has at least two ventilation coils (60, 62, f64), the distance between them is equal to its diameter that the'Elektronenabgabequelle in the one ventilation rinse (60) (22 a) is arranged and that the other air core coil (62, 64) comprises the opening (26 a, 28 a). 1 sheet of drawings